Apparatus and method for providing a task reminder based on travel history

ABSTRACT

An apparatus for providing a task reminder to be performed at a task location includes a monitoring module that monitors a location of a user via a mobile communication device associated with the user at predetermined time intervals for tracking historical travel information of the user, and a data store for storing the historical travel information and for storing user specified task information that includes a task and a task location. In an exemplary embodiment, the apparatus includes a reminder module that is configured to determine a reminder position as a position where an estimated probability of the user traveling from the reminder position at a particular time in a trajectory leading away from the task location exceeds an estimated probability of the user traveling from the reminder position at that same time in a trajectory leading toward the task location by a threshold value. The reminder module generates a reminder of the task when the reminder position is identified.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 11/536,306, filed on Sep. 28, 2006 now U.S. Pat. No. 7,528,713,entitled “APPARATUS AND METHOD FOR PROVIDING A TASK REMINDER BASED ONTRAVEL HISTORY”, which is related to U.S. patent application Ser. No.11/536,232, filed on Sep. 28, 2006 now U.S. Pat. No. 7,649,454, entitled“METHOD AND SYSTEM FOR PROVIDING A TASK REMINDER”, filed concurrentlywith U.S. patent application Ser. No. 11/536,306 and commonly owned andherein incorporated by reference.

BACKGROUND

Handheld electronic devices, such as personal digital assistants (PDAs),mobile phones, digital cameras, and the like, offer mobility and avariety of services to their respective users. While they are typicallyconfigured to transmit and receive data to and from other devices via awired or wireless connection, most mobile communication devices can alsoprovide Internet access, maintain a personal address book, providemessaging capabilities, capture digital images, and place phone calls.Many devices, in particular smart phones and PDAs, provide a calendaringand/or “to-do list” function that allows the user to calendarappointments and to enter tasks directly into the device or into aservice in a remote server. The calendaring function can be configuredto provide a reminder of an appointment or task to the user at or nearthe time the appointment has been scheduled.

Many mobile communication devices can also identify their respectivelocations within a certain range depending on the device and locationidentifying technique. Some devices can use a sophisticated positiondetermining system, such as a Global Positioning System (GPS). The GPSis a satellite-based radio navigation system that uses signals fromthree or four satellites to compute the current latitude, longitude andelevation of a GPS receiver in the device anywhere on earth down towithin a few meters. Other devices can use a location identifyingtechnique based on which base station is servicing the device, that is,the location of the device is within a range of the base station fromwhich a call is made. Other devices can use location identifyingtechniques based on triangulation between the device and at least twobase stations.

The device's location, typically represented by geospatial coordinates,can be used in a variety of ways. For example, a mapping service can usethe device's current location to provide street directions from thecurrent location to a desired destination location. In addition, astreet address or name corresponding to the geospatial coordinates canbe associated with a task or an appointment that is scheduled to beperformed at or near the location. For example, the user can associate atask on the to-do list, e.g., “pick up medicine,” with the streetaddress or geospatial coordinates associated with a task location, e.g.,the user's pharmacy. When the device detects that the user is within acertain distance of the task location, e.g., the pharmacy, the devicecan display a message reminding the user to perform the task, e.g.,“pick up medicine.” Alternatively, a reminder can be issued when thedevice detects that the user is near the task location and is travelingin a trajectory leading to the task location.

Location-based task reminders are useful for prompting the user toperform tasks that are located nearby. Typically, the reminders aregenerated when the user comes within a predetermined fixed distance ofthe task location and or when the user is traveling in a trajectoryleading to the task location within the predetermined distance. This canbe problematic, however, when the user does not routinely travel withinthe predetermined distance of task location. For example, if the userroutinely travels a particular route and the task location is notlocated within the predetermined distance of the route, the user maynever receive a task reminder unless he breaks away from the familiarroute and travels within the predetermined distance of the tasklocation. As a result, the user might forget to perform the task or missan appointment.

To address this problem, some services allow the user to enter areminder distance when the user calendars the task and task location.This approach, however, may not be helpful if the user is unfamiliarwith the task location, or if another person other than the user iscalendaring the task for the user. In any event, requiring the user toprovide information in addition to the task/appointment and tasklocation can be time-consuming and inconvenient.

SUMMARY

Accordingly, an apparatus and method for providing a task reminder to beperformed at a task location are described. According to one exemplaryembodiment, the apparatus includes a monitoring module that monitors alocation of a user via a mobile communication device associated with theuser at predetermined time intervals for tracking historical travelinformation of the user, and a data store for storing the historicaltravel information and for storing user specified task information thatincludes a task and a task location. In an exemplary embodiment, theapparatus includes a reminder module that is configured to determine areminder position as a position where an estimated probability of theuser traveling from the reminder position at a particular time in atrajectory leading away from the task location exceeds an estimatedprobability of the user traveling from the reminder position at thatsame time in a trajectory leading toward the task location by athreshold value. The reminder module generates a reminder of the taskwhen the reminder position is identified.

According to another exemplary embodiment, a method of providing a taskreminder to be performed at a task location includes tracking historicaltravel information of a user of a mobile communication device bymonitoring a location of the user via the mobile communication device atpredetermined time intervals, receiving user specified task informationthat includes a task and a task location, and storing the user'shistorical travel information and user specified task information in adata store. The method further includes determining a reminder positionas a position where an estimated probability of the user traveling fromthe reminder position at a particular time in a trajectory leading awayfrom the task location exceeds an estimated probability of the usertraveling from the reminder position at that same time in a trajectoryleading toward the task location by a threshold value, and generating areminder of the task when the reminder position is identified.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings provide visual representations which will beused to more fully describe the representative embodiments disclosedhere and can be used by those skilled in the art to better understandthe representative embodiments and their inherent advantages. In thesedrawings, like reference numerals identify corresponding elements, and:

FIG. 1 is a block diagram illustrating an exemplary task reminder systemaccording to an exemplary embodiment;

FIGS. 2-4 are more detailed block diagrams illustrating the taskreminder system according to several exemplary embodiments;

FIG. 5 is a flow diagram illustrating an exemplary process for providinga task reminder according to an exemplary embodiment;

FIG. 6 is a block diagram illustrating an exemplary region comprising aplurality of contiguous non-overlapping cells according to an exemplaryembodiment;

FIG. 7 is a block diagram illustrating an exemplary reminder moduleaccording to an exemplary embodiment;

FIG. 8A and FIG. 8B are block diagrams illustrating exemplary targetcells according to exemplary embodiments;

FIG. 9 is a flow diagram illustrating an exemplary process fordetermining whether a target cell is a reminder position according toone embodiment;

FIG. 10A and FIG. 10B are block diagrams illustrating exemplary forwardand backward cells according to exemplary embodiments; and

FIG. 11 is a flow diagram illustrating an exemplary process fordetermining whether a target cell is a reminder position according toanother embodiment.

DETAILED DESCRIPTION

Various aspects will now be described in connection with exemplaryembodiments, including certain aspects described in terms of sequencesof actions that can be performed by elements of a computing device orsystem. For example, it will be recognized that in each of theembodiments, at least some of the various actions can be performed byspecialized circuits or circuitry (e.g., discrete and/or integratedlogic gates interconnected to perform a specialized function), byprogram instructions being executed by one or more processors, or by acombination of both. Thus, the various aspects can be embodied in manydifferent forms, and all such forms are contemplated to be within thescope of what is described.

According to an exemplary embodiment, intelligent, situation-sensitivetask reminders are generated for a user of a mobile communicationdevice. In one embodiment, a task reminder for a task is generatedbefore the user arrives at a position where the user would tend to veeraway from a task location associated with the task. By providing thetask reminder before the user arrives at that position, the user canchoose to deviate from the routine route (which leads away from the tasklocation) and travel in a trajectory that leads toward the tasklocation.

In one embodiment, the historical travel information of the user inrelation to a position is analyzed to determine whether a task remindershould be generated. According to an exemplary embodiment, thehistorical travel information is used to calculate the respectiveprobabilities of the user traveling from the position in a trajectoryleading away from and toward the task location. When the probability oftraveling away from the task location exceeds the probability oftraveling toward the task location by a threshold value, a task remindercan be generated. In one embodiment, the task reminder is generated whenthe position is within a predetermined distance of the user's currentposition.

FIG. 1 is a block diagram illustrating an exemplary arrangement for atask reminder system 100 according to one embodiment. One or morenetwork-enabled mobile communication devices 110, such as a digitalcamera/phone, PDA, laptop or the like, are in communication with areminder server 300 over a network 10. A data store 150 includes generalgeospatial information relating to a plurality of locations and isaccessed by the device 110 or the reminder server 300 over the network10. The general geospatial information 150 is typically publicinformation that can include geographical information 152 that mapsgeospatial coordinates to street names and building names. Thegeospatial information 150 can also include one or more directories 154that provide other information associated with street addresses. Wellknown mapping services (not shown) can use the geospatial information150 to generate traveling routes between two locations, and to determinea distance between two locations.

According to an exemplary embodiment, the system 100 includes means formonitoring a location of a user 120 via a mobile communication device110 associated with the user 120 at predetermined time intervals, suchas a monitoring module 200 that is in communication with the devices 110and with the reminder server 300 over the network 10. In an exemplaryembodiment, the monitoring module 200 monitors the location of the user120 in order to track the historical travel information of the user 120.

The system further includes means for receiving user specified taskinformation, which includes a task and a task location, and means forstoring user-specific information that includes the historical travelinformation of the user 120 and the user specified task information. Forexample, in an exemplary embodiment, the monitoring module 200 isconfigured to store and manage the user-specific information in a datastore 220.

FIG. 2 is a more detailed block diagram of the reminder system 100according to an exemplary embodiment. Each device 110 includes circuitrythat can track a position of the device 110. For example, the device 110can include a position locator system 112 that tracks the position ofthe device 110. The position locator system 112 can be the well knownglobal positioning system (GPS) that utilizes satellites 140 (FIG. 1) todetermine the device's longitudinal and latitudinal position.Alternatively, the position locator system 112 can be configured toutilize one or more base stations 130 within communication range todetermine the device's location. Each mobile communication device 110also includes circuitry for communicating with the reminder server 300and monitoring module 200. For example, the device 110 can include acommunication interface 118 coupled to a user interface 121 andinput/output (I/O) module 114 that allows the user 120 to use the device110 to communicate with the server 300 over a wireless network 10 usingone or more communication protocols.

The monitoring module 200 can be a personal computer or other devicecapable of collecting, storing and managing data. The monitoring module200 can include a communication interface (not shown) to receive andtransmit data over the network 10. In one embodiment, the monitoringmodule 200 monitors the location of the device 110 at predetermined timeintervals in order to track the user's historical travel information222. The historical travel information 222 can include the number oftimes the user 120 is present at or near a location, the amount of timethe user 120 is present at or near the location, the number of times theuser 120 has changed his or her position between at least two locations,and/or the number of times the user 120 has entered or exited a region.The historical travel information 222 is stored in the data store 220along with the task information 224.

The reminder server 300 can be a personal computer or other devicecapable of processing data. The reminder server 300 includes acommunication interface 302 to transmit and receive data over thenetwork 10. In one embodiment, the reminder server 300 is configured toretrieve user-specific information from the data store 220 over thenetwork 10 via the monitoring module 200.

The system 100 further includes means for generating a reminder of atask based on the user's historical travel information. For example,according to an exemplary embodiment, the reminder server 300 includes areminder module 310 which is communicatively coupled to thecommunication interface 302. The reminder module 310 is configured todetermine whether it would be useful to generate a task reminder for theuser 120 based on the user's current position and the user's historicaltravel patterns in a region including the user's current position andthe task location.

In one embodiment, a task reminder is generated when the reminder module310 identifies a reminder position near the user's current position. Inan exemplary embodiment, a reminder position is a position where anestimated probability of the user 120 traveling from the reminderposition at a particular time in a trajectory leading away from the tasklocation exceeds an estimated probability of the user 120 traveling fromthe reminder position at that same time in a trajectory leading towardthe task location by a threshold value. When the reminder module 310identifies a position that satisfies the criteria for a reminderposition, the task reminder is generated and transmitted to the user120.

The system 100 illustrated in FIG. 1 and FIG. 2 is but one exemplaryarrangement. In this arrangement, a “thin” mobile communication device110 can be accommodated because the historical travel information 222and task information 224 can be stored remotely and the functionality ofthe monitoring module 200 and the reminder module 310 can be included inseparate servers. Other arrangements can be designed by those skilled inthe art. For example, in one embodiment shown in FIG. 3, thefunctionality of the monitoring module 200 and the data store 220 can beincluded in the reminder server 300 b so that the reminder server 300 bsecurely manages the user-specific information 220.

In another embodiment, shown in FIG. 4, the mobile communication device110 c can perform the functions of the reminder module 310 and themonitoring module 200, and store the user-specific information 220internally in the device memory (not shown). In this arrangement, thereminder server 300 is not required. Variations of these embodiments maybe utilized and structural and functional modifications may be madewithout departing from the scope of the present disclosure. For example,the functionality of the monitoring module 200 can be integrated withthat of the mobile communication device 110 and can be configured totransmit the historical travel information 222 to the reminder module310, which stores and manages the information in the data store 220. Inthis example, the reminder module 310 can also be configured to receiveand store the task information 224 directly from the mobilecommunication device 110, and can manage the information in the datastore 220.

FIG. 5 is a flow diagram illustrating an exemplary process for providinga task reminder according to one embodiment. Referring to FIGS. 1-4, theexemplary process begins when user-specified task information 224 isreceived and stored in the data store 220 (step 500). In one embodiment,the task information 224 includes a description that describes the taskand at least one task location that indicates where the task can beperformed. For example, if the task is to “buy organic apples,” the taskinformation can identify several organic grocery stores where the user120 can perform the task. In addition, the task information 224 canindicate a priority level, a time frame in which the task should becompleted, with whom the task should be performed, and any otherinformation related to the task, e.g., prescription number, phone numberto call, etc. A task location can be represented by any one of thegeospatial coordinates of the task location, a street address, and alocation name.

In one embodiment, the user 120 specifies the task information 224 usinga network enabled device, such as the mobile communication device 110,and sends the task information 224 to the reminder module 310 in thereminder server 300 or to the monitoring module 200 over the network 10via the communication interface 118. The task information 224 is thenorganized in a task list 226. In one embodiment, the task list 226includes at least one task and a reference to the associated taskinformation. The tasks can be sorted in the order in which they werereceived, by priority/importance, by time frame, or by any othersuitable factor.

Referring again to FIG. 5, in addition to receiving and storing the taskinformation 224, the location of the mobile communication device 110 ismonitored at predetermined time intervals and the historical travelinformation is stored in the data store 220 (step 502). In oneembodiment, an entire geographical area of interest is represented by aplurality of contiguous cells, where different cells do not overlap. Theuser's position can be identified by geospatial coordinates generated bythe position locator system 112 in the device 110 or provided by theuser 120 via the I/O module 114. The geospatial coordinates of theuser/device 110 can be used to identify the cell in which the user'sposition is located so that the historical travel information of theuser 120 can be tracked.

In one embodiment, the monitoring module 200 monitors the device'slocation and collects the historical travel information 222 of the userby querying the position locator system 112 in the device 110 at a fixedtime interval or sampling interval. For example, the monitoring module200 can collect the travel information 222 every two minutes. In anotherembodiment, the monitoring module 200 can collect the information 222 ata sampling interval proportional to a velocity or expected velocity ofthe mobile communication device 110. For example, if the mobilecommunication device 110 is installed in a car, the sampling intervalcan be based on the average velocity of the car.

For each of the plurality of cells, the monitoring module 200 collectstransition information associated with a cell. In one embodiment, thetransition information includes a number of times the user 120 movesfrom the cell to any other cell, or remains within the same cell, duringconsecutive sampling intervals. For example, consider an exemplaryregion that is represented by a plurality of contiguous, non-overlappingcells 600 illustrated in FIG. 6. As is shown, the monitoring module 200keeps track of the transition information associated with the centercell 600 a over a plurality of sampling intervals. According to thisexample, the transition information indicates that the user 120 hasmoved from the center cell 600 a to the westward adjacent cell (600W) 13times, to the eastward adjacent cell (600E) 2 times, to the northwardadjacent cell (600N) 7 times, and to the southward adjacent cell (600S)1 time. In addition, the user 120 has stayed in the same cell 44 times.This transition information, referred to above as the historical travelinformation 222 of the user 120, is stored in the data store 220.

According to an exemplary embodiment, after the historical travelinformation 222 is stored, the reminder module 310 considers a firsttask on the task list 226 (block 504). A target cell evaluator module312 in the reminder module 310, shown in FIG. 7, identifies a pluralityof target cells within a predetermined distance of the user's currentposition (block 506). In one embodiment, the predetermined distance, D,can be proportional to a length, L, of a side of the cell 600, e.g.,D=3L, or proportional to the velocity or expected velocity of the mobilecommunication device 110. The predetermined distance should be largeenough to allow the user 120 sufficient time to choose a trajectorytoward the task location, but small enough to provide a reminder that istimely and meaningful.

In FIG. 8A, the cross-hatched cells are exemplary target cells 650 whenthe user's current position is located in the center cell 600 a and thepredetermined distance, D, is equal to 2L. In another embodiment, a cell600 b can be identified as a target cell 650 when it is within apredetermined distance of the user's current position and when aprobability of the user 120 traveling from the current position to thecell 600 b exceeds a minimum probability threshold value. In oneembodiment, the target cell evaluator 312 uses the transitioninformation associated with the cell 600 a in which the user's currentposition lies, e.g., the center cell 600 a, to calculate the probabilityof the user 120 traveling from the current position to the cell 600 b.

In another embodiment, the target cell evaluator module 312 furtheridentifies the plurality of target cells 650 based on a current travelpattern of the user 120. In this embodiment, the target cell evaluatormodule 312 considers a previous position of the user 120, P₀, and thecurrent position of the user 120, P₁, in determining which cells 600 areidentified as target cells 650. In an exemplary embodiment, illustratedin FIG. 8B, a circle 800 is defined having a center at or near theprevious position, P₀, and having a radius substantially equal to thedistance between the previous position, P₀, and the current position,P₁. As is shown, the current position, P₁, lies on the circle's 800diameter and bisects a segment that defines a sector 850 of the circle800. In one embodiment, the sector 850 has a central angle ofapproximately 60 degrees. The target cells 650 are those cells that arewithin a predetermined distance of the user's current position and thatare not substantially within the sector 850.

Referring again to FIG. 5, once the target cells 650 are identified, thetarget cell evaluator module 312 considers a first target cell 650(block 507) and determines whether the target cell 650 is a reminderposition (block 508). As stated above, a target cell 650 is a reminderposition when an estimated probability of the user 120 traveling fromthe target cell 650 at a particular time in a trajectory leading awayfrom the task location exceeds an estimated probability of the user 120traveling from the target cell 650 at that same time in a trajectoryleading toward the task location by a threshold value.

FIG. 9 is a flowchart illustrating an exemplary process for determiningwhether a target cell 650 is a reminder position according to oneembodiment. The process begins when the target cell evaluator module 312identifies one or more forward cells that are cells that fall within atrajectory leading toward the task location (block 900). In an exemplaryembodiment, the task location is locate in a task cell and each of theplurality of cells 600, including the target cell 650 and the task cell,can be identified by Cartesian coordinates, (x, y), and the target cell650 can be located at an origin, (0, 0).

In one embodiment, illustrated in FIG. 10A, the task cell 620 and thetarget cell 650 can be aligned horizontally, as shown, or vertically(not shown). In this configuration, the forward cells 660 (depicted withforward slashing) can include the cells that fall on the horizontal (orvertical) line from the target cell 650 to the task cell 620 and/or thecells that lie immediately adjacent to the horizontal (or vertical)line. For example, in FIG. 10A, the task cell 620 has coordinates (3,0). Accordingly, the forward cells 660 can include the cells having thecoordinates: (1, 0), (2, 0), (1, 1), (2, 1), (1, −1), and (2, −1).

In another embodiment, illustrated in FIG. 10B, the task cell 620 andthe target cell 650 can be skewed, i.e., not aligned horizontally orvertically. In this configuration, the forward cells 660 can be:

-   -   cells where a sum of absolute values of the cell coordinates is        greater than zero and less than a sum of absolute values of the        task coordinates and whose cell coordinates have the same        polarity as the task coordinates; and/or    -   cells where the x coordinate is at least equal to zero and at        most equal to the x coordinate of the task cell and the y        coordinate is at least equal to zero and at most equal to the y        coordinate of the task cell when the x and y coordinates of the        task cell are each at least equal to zero; and/or    -   cells where the x coordinate is at least equal to zero and at        most equal to the task cell's x coordinate and the y coordinate        is at least equal to the task cell's y coordinate and at most        equal to zero when the task cell's x coordinate is at least        equal to zero and the task cell's y coordinate is less than        zero; and/or    -   cells where the x coordinate is at least equal to the task        cell's x coordinate and at most equal to zero and the y        coordinate is at least equal to the task cell's y coordinate and        at most equal to zero when the task cell's x and y coordinates        are less than zero.        For example, in FIG. 10B, the task cell 620 has coordinates (−3,        1). Accordingly, the forward cells 660 can include the cells        having the coordinates: (−3, 0), (−2, 1), (−2, 0), (−1,2), (−1,        1), (−1, 0), (0, 3), (0, 2), and (0, 1).

Referring again to FIG. 9, once the forward cells 660 have beenidentified, the target cell evaluator module 312 can identify one ormore backward cells that are cells that fall within a trajectory leadingaway the task location (block 902). In an exemplary embodiment, thebackward cells can be identified as reflections of the forward cells660. As used herein, a first cell is a reflection of a second cell whenthe coordinates of the first cell are a mirror reflection of thecoordinates of the second cell. That is, the respective absolute valuesof the x and y coordinates of the first and second cells are the same,but have opposite polarities. For example, when the first cell'scoordinates are (x, y), the reflection cell's coordinates are (−x, −y).

For example, referring again to FIG. 10A, the backward cells 670(depicted with backward slashing) are reflections of the forward cells660 along a vertical mirror plane 665 passing through the origin.Accordingly, the backward cells 670 can include the cells having thecoordinates: (−1, 0), (−2, 0), (−1, −1), (−2, −1), (−1, 1), and (−2, 1).Similarly, referring again to FIG. 10B, the backward cells 670 arereflections of the forward cells 660 along the mirror plane 665.Accordingly, the backward cells 670 can include the cells having thecoordinates: (3, 0), (2, −1), (2, 0), (1, −2), (1, −1), (1, 0), (0, −3),(0, −2), and (0, −1).

Referring again to FIG. 9, once the forward 660 and backward 670 cellshave been identified, the target cell evaluator module 312 calculates aforward probability of the user 120 traveling from the target cell 650in a trajectory leading toward the task position based on the historicaltravel information 222 of the user 120 (block 904). In an exemplaryembodiment, the target cell evaluator module 312 retrieves thehistorical travel information 222 of the user 120 from the data store220 and uses the travel information 222 to calculate the forwardprobability. In one embodiment, the information 222 can be retrieved viathe monitoring module 200. In another embodiment, a data manager 313 inthe reminder module 310, shown in FIG. 7, can retrieve the information222 directly from the data store 220.

In an exemplary embodiment, the transition information associated withthe target cell 650 is used to calculate the forward probability. Asstated above, the transition information for a cell includes the numberof times the user 120 moves from the cell to any other cell, includingthe same cell, during consecutive sampling intervals. In one embodiment,the forward probability can be the sum of the number of times the user120 has traveled from the target cell 650 to any of the forward cells660 divided by a total number of transitions from the target cell 650.

For example, let the transition information illustrated in FIG. 6 beassociated with the target cell 650 illustrated in FIG. 10A, i.e., thecenter cell 600 a in FIG. 6 is the target cell 650 in FIG. 10A. In thisexample, where the task cell 620 has coordinates (3, 0), the sum of thenumber of times the user 120 has traveled from the target cell 650 toany of the forward cells 660 is four (4), and the total number oftransitions from the target cell 650 is 76. Accordingly, the forwardprobability of the target cell 650 is 4/76.

In the embodiment described above, the forward probability is calculatedfrom the transition information that reflects the number of times theuser 120 moves from the target cell 650 directly to any of the forwardcells. In other words, the forward probability reflects the probabilityof the user 120 moving from the target cell 650 to any of the forwardcells 660 in one sampling interval or step. In another embodiment, theforward probability can be based on the number of times the user 120travels from the target cell 650 to any of the forward cells 660 via oneor more cells 600. In other words, the forward probability can reflectthe probability of the user 120 arriving at a forward cell 660 in two ormore steps.

In this embodiment, transition probabilities between cells 600 can berepresented in a transition-probability matrix, M, where the rows of thematrix are “from” cells and the columns of the matrix are “to” cells,and the elements of the transition-probability matrix are the transitionprobabilities. That is, element M[u, v] is the probability oftransitioning from cell “u” to cell “v” in one step.

Let N be a number of steps and let the task cell 620 have coordinates(X, Y), then:N=|X|+|Y|; orN=minimum (|X|,|Y|).In this embodiment, the probability of traveling from cell u to cell vin N steps can be derived by multiplying the transition-probabilitymatrix, M, with itself N times. The resulting N-step transitionprobability matrix, M^(N), includes the probabilities of moving fromcell u to cell v in exactly N steps. In another embodiment, theprobability of traveling from cell u to cell v in up to N steps can bederived by the following:M ^(UP TO N) =M+M ² +M ³ + . . . +M ^(N).

In this embodiment, the forward probability can reflect a more accurateestimate of the user's 120 travel tendencies because a horizon greaterthan a single step is considered. Such probabilities would capture theprobabilities of the user 120 arriving at a forward cell 660, even whenthe user 120 passes through a backward cell 670 or non-backward orforward cell 600, respectively, to get to the forward cell 660.

Referring again to FIG. 9, once the forward probability is calculated(block 904), the target cell evaluator module 312 calculates a backwardprobability of the user 120 traveling from the target cell 650 in atrajectory leading away from the task position based on the historicaltravel information of the user 120 (block 906). In an exemplaryembodiment, the backward probability is calculated in the same mannerdescribed for calculating the forward probability. That is, the backwardprobability can be the sum of the number of times the user 120 hastraveled from the target cell 650 to any of the backward cells 670divided by a total number of transitions from the target cell 650. Forexample, referring again to the transition information shown in FIG. 6,the sum of the number of times the user 120 has traveled from the targetcell 650 to any of the backward cells 670 is 20, and the total number oftransitions from the target cell 650 is 76. Accordingly, the backwardprobability of the target cell 650 is 20/76. Alternatively, in anotherembodiment, the backward probability can be based on the number of timesthe user 120 travels from the target cell 650 to any of the backwardcells 670 via one or more cells 600.

In an exemplary embodiment, the target cell evaluator 312 then subtractsthe forward probability from the backward probability (block 910) andcompares the difference to the threshold value (block 912). If thedifference is greater than the threshold value, the target cellevaluator module 312 designates the target cell 650 as a reminderposition (block 914). Conversely, if the difference is less than thethreshold value, the target cell 650 is not so designated (block 916).

Referring again to FIG. 5, when the target cell evaluator module 312determines that the target cell 650 is not a reminder position (block510), the reminder module 310 determines whether more target cells needto be analyzed (block 514) and if such is the case, goes to the nexttarget cell 650 (block 515) and repeats the process described in blocks508 and 510.

When the target cell evaluator module 312 determines that the targetcell 650 is a reminder position (block 510), the reminder module 310 cancall a message generator module 314, shown in FIG. 7, which isconfigured to generate and send the task reminder to the user 120 viathe mobile communication device (block 512). In one embodiment, themessage generator module 314 can first determine whether the user 120 isavailable to receive the reminder. In one embodiment, the user 120 isavailable when she is actively using the mobile communication device 110or has recently used the device 110 within a specified time period,e.g., 10 seconds. In one embodiment, the message generator module 314can call the monitoring module 200 to make this determination.

If the user 120 is using or has recently used the device 110, e.g., bytaking pictures or sending messages to others, the message generatormodule 314 can send a message that includes the task reminder to theuser 120 during use or immediately after the user 120 has stoppedactively using the device 110. Otherwise, the message generator module314 can wait until the user 120 is available. In one embodiment, whenthe task reminder for a task has been sent, the message generator module314 is configured to prevent a subsequent task reminder for the sametask to be sent unless a predetermined time period has expired and/or adistance between the user 120 and the task cell 620 has not reduced tozero, but has exceed a threshold distance that is greater than thepredetermined distance.

After the task reminder has been sent or when the reminder module 310determines that all target cells 650 have been analyzed (block 514)without generating a reminder, the reminder module 310 determineswhether more tasks remain on the task list 226 to be processed (block516). If no other tasks remain, the process returns to monitoring thedevice's location (block 502). Otherwise, the next task is considered(block 518) and the process repeats at block 507 where the first targetcell 650 is considered with respect to the next task.

As mentioned above, the tasks on the task list 226 can be listed inorder of importance, time for completion, or any other suitable factor.Accordingly, the task reminder process can be performed for tasksaccording to their respective importance or completion time. Thereminder module 310 can perform the process for a task with a highestpriority, or it can process each of the tasks in order of decreasingpriority.

Although the process above in FIG. 5 has been described for a taskassociated with one task location, the process can be applied equally toa task associated with more than one task location. For example, a taskhaving two task locations located in two different task cells can betreated as two subtasks, and the process can be performed for each tasklocation.

In another exemplary embodiment, the process can be performed once for atask associated with a plurality of task locations. In this embodiment,the process for determining whether the target cell 650 is a reminderposition considers each of the task locations together. For example,FIG. 11 is a flowchart illustrating an exemplary process for determiningwhether a target cell 650 is a reminder position when a task isassociated with a plurality of task locations according to an exemplaryembodiment. The process begins when the target cell evaluator module 312identifies one or more forward cells 660 for each of the task locationslocated in one or more task cells 620. (block 1100). In one embodiment,the forward cells 660 are identified in the same manner described above.Next, the target cell evaluator module 312 identifies one or morebackward cells 670 for each of the task cells 620 (block 1102).

Once the forward cells 660 and backward cells 670 have been identified,the target cell evaluator module 312 considers a first of the pluralityof task cells 620 (block 1104) and calculates a forward probability ofthe user 120 traveling from the target cell 650 in a trajectory leadingtoward the first task cell 620 (block 1106). In one embodiment, theforward probability is calculated by summing a number of times the user120 has transitioned from the target cell 650 to any of the forwardcells 660 associated with the first task cell 620 and dividing the sumby a total number of transitions from the target cell 650.

The target cell evaluator 312 then identifies one or more strongbackward cells (block 1108). In this embodiment, a strong backward cellis a backward cell associated with the first task cell 620 that is notalso identified as a forward cell 660 for any of the other task cells620. The target cell evaluator module 312 then calculates a strongbackward probability of the user 120 traveling from the target cell 650in a trajectory leading away from the first task cell 620 (block 1110).In one embodiment, the strong backward probability is calculated bysumming a number of times the user 120 has transitioned from the targetcell 650 to any of the strong backward cells 660 associated with thefirst task cell 620 and dividing the sum by a total number oftransitions from the target cell 650.

In an exemplary embodiment, the target cell evaluator 312 then subtractsthe forward probability from the strong backward probability (block1112) and compares the difference to the threshold value (block 1114).If the difference is greater than the threshold value, the target cellevaluator module 312 designates the target cell 650 as a reminderposition (block 1116). Conversely, if the difference is less than thethreshold value, the target cell evaluator module 312 determines whethermore task cells 620 need to be analyzed (block 1118). If such is thecase, the next task cell is considered (block 1120) and the processrepeats at block 1106 where the forward probability for the next taskcell 620 is calculated. When all the task cells 620 have been analyzed(block 1118) and none have resulted in a target cell designation, thetarget cell 650 is a reminder position (block 1122).

In another embodiment, instead of considering a task cell 650individually, the target cell evaluator module 312 aggregates the taskcells 650 and calculates an aggregate forward probability by summing thenumber of times the user 120 has transitioned from the target cell 650to any of the one or more forward cells 660 associated with any taskcell 620 and dividing the sum by the total transitions. Similarly, anaggregate backward probability is calculated by summing the number oftimes the user 120 has transitioned from the target cell 650 to any ofthe one or more backward cells 670 associated with any task cell 620 anddividing the sum by the total transitions. The aggregate forwardprobability is then subtracted from the aggregate backward probabilityand the difference is compared to the threshold value.

As stated above, when a reminder position is identified, the remindermodule generates and sends a message including the task reminder to theuser 120. In one embodiment, when the task reminder is sent, the device110 receives the message via the communication interface 118 and themessage is displayed to the user 120 on the device's user interface 121.The user 120 can respond to the task reminder explicitly and implicitly.In one embodiment, the user 120 can respond positively by explicitly“accepting” the reminder using the mobile communication device 110.Alternatively, or in addition to, the user 120 can implicitly respondpositively by traveling to the task location within a certain timeperiod after receiving the message and optionally remaining at or nearthe task location for a period of time. Similarly, the user 120 canrespond negatively by explicitly “rejecting” the reminder or by movingaway from the task location.

According to an exemplary embodiment, the reminder module 310 canreceive or monitor the user's response to the task reminder and adjustthe threshold value based on the user's response. For example, in oneembodiment, the threshold value can be lowered when the user 120responds positively to the reminder and can be increased when the user120 responds negatively to the reminder. In another embodiment, thereminder module 310 can adjust the threshold value based on theimportance of the task, as indicated explicitly or by name. For example,the threshold value can be lowered as the importance of the taskincreases. In yet another embodiment, the threshold value can be basedon the time frame in which the task is to be completed where thethreshold value is lowered as the time frame becomes smaller.

The executable instructions of a computer program as illustrated in FIG.5, FIG. 9 and FIG. 11 can be embodied in any computer readable mediumfor use by or in connection with an instruction execution system,apparatus, or device, such as a computer based system, processorcontaining system, or other system that can fetch the instructions fromthe instruction execution system, apparatus, or device and execute theinstructions.

As used here, a “computer readable medium” can be any means that cancontain, store, communicate, propagate, or transport the program for useby or in connection with the instruction execution system, apparatus, ordevice. The computer readable medium can be, for example, but is notlimited to, an electronic, magnetic, optical, electromagnetic, infrared,or semiconductor system, apparatus, device, or propagation medium.

More specific examples (a non-exhaustive list) of the computer readablemedium can include the following: a wired network connection andassociated transmission medium, such as an ETHERNET transmission system,a wireless network connection and associated transmission medium, suchas an IEEE 802.11 (a), (b), or (g) or a BLUETOOTH transmission system, awide-area network (WAN), a local-area network (LAN), the Internet, anintranet, a portable computer diskette, a random access memory (RAM), aread only memory (ROM), an erasable programmable read only memory (EPROMor Flash memory), an optical fiber, a portable compact disc (CD), aportable digital video disc (DVD), and the like.

It will be appreciated by those of ordinary skill in the art that theconcepts and techniques described here can be embodied in variousspecific forms without departing from the essential characteristicsthereof. The presently disclosed embodiments are considered in allrespects to be illustrative and not restrictive. The scope of theinvention is indicated by the appended claims, rather than the foregoingdescription, and all changes that come within the meaning and range ofequivalence thereof are intended to be embraced.

What is claimed is:
 1. An apparatus for providing a reminder of a taskto be performed at a task location, the apparatus comprising: amonitoring module configured to monitor a location of a user via amobile communication device associated with the user at predeterminedtime intervals for tracking historical travel information of the user; adata store for storing the user's historical travel information and forstoring user specified task information that includes a task and a tasklocation; and a reminder module configured to determine a reminderposition as a position where an estimated probability of the usertraveling from the reminder position at a particular time in atrajectory leading toward the task location exceeds an estimatedprobability of the user traveling from the reminder position at thatsame time in a trajectory leading away from the task location by athreshold value, and to generate a reminder for the task when thereminder position is identified.
 2. The apparatus of claim 1 wherein thetask location is in a region that comprises a plurality of contiguouscells, and wherein the monitoring module is configured to identify inwhich cell of the plurality of cells the user is located at thepredetermined time intervals.
 3. The apparatus of claim 2 wherein theuser's historical travel information includes transition information foreach cell of the plurality of cells, wherein the transition informationof a cell includes respective numbers of times the user transitions fromthe cell to other cells.
 4. The apparatus of claim 3 wherein thereminder generation module is configured to determine the reminderposition by identifying a target cell that is within a predetermineddistance of a current position of the user, identifying one or moreforward cells that are in a trajectory leading from the target cell tothe task location in a task cell, and identifying one or more backwardcells that are in a trajectory from the target cell leading away fromthe task cell.
 5. The apparatus of claim 4 wherein when the task celland the target cell are aligned horizontally or vertically, the one ormore forward cells are at least one of cells that lie on a horizontal orvertical line from the target cell to the task cell and cells that lieimmediately adjacent to the horizontal line or the vertical line, andthe one or more backward cells are reflections of the one or moreforward cells.
 6. The apparatus of claim 5 wherein the target cell isrepresented as an origin and each cell is represented by first andsecond cell coordinates and the task cell is represented by first andsecond task coordinates relative to the origin, and wherein the one ormore forward cells are not the origin and at least one of: cells where asum of absolute values of the cell coordinates is greater than zero andless than a sum of absolute values of the task coordinates and whosecell coordinates have the same polarity as the task coordinates when thetask cell and the target cell are not aligned horizontally orvertically; cells where the first cell coordinate is at least equal tozero and at most equal to the first task coordinate and the second cellcoordinate is at least equal to zero and at most equal to the secondtask coordinate when the first and second task coordinates are each atleast equal to zero; cells where the first cell coordinate is at leastequal to zero and at most equal to the first task coordinate and thesecond cell coordinate is at least equal to the second task coordinateand at most equal to zero when the first task coordinate is at leastequal to zero and the second task coordinate is less than zero; cellswhere the first cell coordinate is at least equal to the first taskcoordinate and at most equal to zero and the second cell coordinate isat least equal to zero and at most equal to the second task coordinatewhen the first task coordinate is less than zero and the second taskcoordinate is at least equal to zero; and cells where the first cellcoordinate is at least equal to the first task coordinate and at mostequal to zero and the second cell coordinate is at least equal to thesecond task coordinate and at most equal to zero when the first andsecond task coordinates are less than zero.
 7. The apparatus of claim 4wherein the reminder module is configured to calculate a forwardprobability of the user traveling from the target cell in a trajectoryleading toward the task position and to calculate a backward probabilityof the user traveling from the target cell in a trajectory leading awayfrom the task position based on the transition information for thetarget cell.
 8. The apparatus of claim 7 wherein the reminder module isconfigured to calculate the forward probability by summing a number oftimes the user has transitioned from the target cell to any of the oneor more forward cells and dividing the sum by a total number oftransitions from the target cell, and to calculate the backwardprobability by summing a number of times the user has transitioned fromthe target cell to any of the one or more backward cells and dividingthe sum by the total number of transitions from the target cell.
 9. Theapparatus of claim 8 wherein the reminder module is configured todesignate the target cell as a reminder position when the forwardprobability exceeds the backward probability by the threshold value. 10.The apparatus of claim 7 wherein the reminder module is configured tocalculate the forward probability based on the number of times the userhas traveled from the target cell to any of the one or more forwardcells via one or more cells, and to calculate the backward probabilitybased on the number of times the user has traveled from the target cellto any of the one or more backward cells via one or more cells.
 11. Theapparatus of claim 3 wherein the reminder generation module isconfigured to determine the reminder position by identifying one or moretarget cells, wherein a target cell is within a predetermined distanceof a current position of the user and a probability of the usertraveling from the current position to the target cell exceeds a minimumprobability threshold, and analyzing the one or more target cells indescending order of their probability.
 12. The apparatus of claim 4wherein the target cell is further based on a current traveling patternof the user.
 13. The apparatus of claim 4 wherein the reminder module isfurther configured to transmit the reminder for the task to the user viathe mobile communication device and to prevent a subsequent reminder forthe task unless at least one of a predetermined time thereafter hasexpired, and a distance between the user and the task cell has notreduced to zero, but has exceeded a threshold distance that is greaterthan the predetermined distance.
 14. The apparatus of claim 3 whereinthe task is associated with a plurality of task locations located in oneor more task cells and the reminder generation module is configured todetermine the reminder position by identifying a target cell that iswithin a predetermined distance of a current position of the user,identifying one or more forward cells for each of the one or more taskcells, wherein for each task cell, the one or more forward cells are ina trajectory leading from the target cell to the task cell, andidentifying one or more backward cells for each of the one or more taskcells, wherein for each task cell, the one or more backward cells are ina trajectory from the target cell leading away from the task cell. 15.The apparatus of claim 14 wherein the reminder module is furtherconfigured to identify for a first task cell of the one or more taskcells one or more strong backward cells comprising backward cellsassociated with the first task cell that are not identified as forwardcells for other of the one or more task cells, to calculate a forwardprobability of the user traveling from the target cell in a trajectoryleading toward the first task cell by summing a number of times the userhas transitioned from the target cell to any of the one or more forwardcells associated with the first task cell and dividing the sum by atotal number of transitions from the target cell, to calculate abackward probability of the user traveling from the target cell in atrajectory leading away from the first task cell by summing a number oftimes the user has transitioned from the target cell to any of the oneor more strong backward cells and dividing the sum by the total numberof transitions from the target cell, and to designate the target cell asa reminder position when the forward probability exceeds the backwardprobability by the threshold value.
 16. The apparatus of claim 14wherein the reminder module is further configured to calculate a forwardprobability of the user traveling from the target cell in a trajectoryleading toward any task cell by summing a number of times the user hastransitioned from the target cell to any of the one or more forwardcells and dividing the sum by a total number of transitions from thetarget cell, to calculate a backward probability of the user travelingfrom the target cell in a trajectory leading away from any task cell bysumming a number of times the user has transitioned from the target cellto any of the one or more backward cells and dividing the sum by thetotal number of transitions from the target cell, and to designate thetarget cell as a reminder position when the forward probability exceedsthe backward probability by the threshold value.
 17. The apparatus ofclaim 1 wherein the user specified task information includes a pluralityof tasks and wherein the reminder module is configured to prioritize theplurality of tasks based on at least one of task importance andcompletion time, and to determine a reminder position for a tasklocation associated with a task having a highest priority.
 18. Theapparatus of claim 17 wherein the reminder module is further configuredto determine a reminder position for respective task locationsassociated with each of the plurality of tasks in order of decreasingpriority.
 19. The apparatus of claim 1 wherein the apparatus is a mobilecommunication device comprising: a communication interface coupled to anetwork; and a position locator system configured to identify thelocation of the mobile communication device.
 20. The apparatus of claim19 wherein the monitoring module is configured to query the positionlocator system to identify the location of the mobile communicationdevice at least one of at a fixed sampling interval and at a samplinginterval proportional to at least one of a velocity and an expectedvelocity of the mobile communication device.
 21. The apparatus of claim1, wherein the apparatus is a server comprising: a communicationinterface for communicating with the mobile communication deviceassociated with the user over a network and configured to receive userspecified task information and the location of the mobile communicationdevice.
 22. A method of providing a reminder of a task to be performedat a task location, the method comprising: monitoring a location of auser via a mobile communication device associated with the user atpredetermined time intervals for tracking historical travel informationof the user; receiving user specified task information that includes atask and a task location; storing the user's historical travelinformation and user specified task information in a data store;determining a reminder position as a position where an estimatedprobability of the user traveling from the reminder position at aparticular time in a trajectory leading toward the task location exceedsan estimated probability of the user traveling from the reminderposition at that same time in a trajectory leading away from the tasklocation by a threshold value; and generating a reminder for the taskwhen the reminder position is identified.
 23. The method of claim 22wherein the task location is in a region that comprises a plurality ofcontiguous cells, and wherein monitoring includes identifying in whichcell of the plurality of cells the user is located at the predeterminedtime intervals.
 24. The method of claim 23 wherein monitoring user'slocation includes collecting transition information for each cell of theplurality of cells, wherein the transition information of a cellincludes respective numbers of times the user transitions from the cellto other cells.
 25. The method of claim 24 wherein determining thereminder position includes: identifying a target cell that is within apredetermined distance of a current position of the user; identifyingone or more forward cells that are in a trajectory leading from thetarget cell to the task location in a task cell; and identifying one ormore backward cells that are in a trajectory from the target cellleading away from the task cell.
 26. The method of claim 25 wherein whenthe task cell and the target cell are aligned horizontally orvertically, identifying the one or more forward cells includesidentifying at least one of cells that lie on a horizontal or verticalline from the target cell to the task cell and cells that lieimmediately adjacent to the horizontal line or the vertical line, andidentifying the one or more backward cells includes identifying cellsthat are reflections of the one or more forward cells.
 27. The method ofclaim 26 wherein the target cell is represented as an origin and eachcell is represented by first and second cell coordinates and the taskcell is represented by first and second task coordinates relative to theorigin, wherein the one or more forward cells are not the origin, andwherein identifying the one or more forward cells includes identifyingat least one of: cells where a sum of absolute values of the cellcoordinates is greater than zero and less than a sum of absolute valuesof the task coordinates and whose cell coordinates have the samepolarity as the task coordinates when the task cell and the target cellare not aligned horizontally or vertically; cells where the first cellcoordinate is at least equal to zero and at most equal to the first taskcoordinate and the second cell coordinate is at least equal to zero andat most equal to the second task coordinate when the first and secondtask coordinates are each at least equal to zero; cells where the firstcell coordinate is at least equal to zero and at most equal to the firsttask coordinate and the second cell coordinate is at least equal to thesecond task coordinate and at most equal to zero when the first taskcoordinate is at least equal to zero and the second task coordinate isless than zero; cells where the first cell coordinate is at least equalto the first task coordinate and at most equal to zero and the secondcell coordinate is at least equal to zero and at most equal to thesecond task coordinate when the first task coordinate is less than zeroand the second task coordinate is at least equal to zero; and cellswhere the first cell coordinate is at least equal to the first taskcoordinate and at most equal to zero and the second cell coordinate isat least equal to the second task coordinate and at most equal to zerowhen the first and second task coordinates are less than zero.
 28. Themethod of claim 25 wherein identifying the reminder position includescalculating a forward probability of the user traveling from the targetcell in a trajectory leading toward the task position and calculating abackward probability of the user traveling from the target cell in atrajectory leading away from the task position based on the transitioninformation for the target cell.
 29. The method of claim 28 whereincalculating the forward probability includes summing a number of timesthe user has transitioned from the target cell to any of the one or moreforward cells and dividing the sum by a total number of transitions fromthe target cell, and calculating the backward probability includessumming a number of times the user has transitioned from the target cellto any of the one or more backward cells and dividing the sum by thetotal number of transitions from the target cell.
 30. The method ofclaim 29 wherein identifying the reminder position includes designatingthe target cell as a reminder position when the forward probabilityexceeds the backward probability by the threshold value.
 31. The methodof claim 28 wherein calculating the forward probability includescounting the number of times the user has traveled from the target cellto any of the one or more forward cells via one or more cells, andcalculating the backward probability includes counting the number oftimes the user has traveled from the target cell to any of the one ormore backward cells via one or more cells.
 32. The method of claim 24wherein determining the reminder position includes identifying one ormore target cells, wherein a target cell is within a predetermineddistance of a current position of the user and a probability of the usertraveling from the current position to the target cell exceeds a minimumprobability threshold, and analyzing the one or more target cells indescending order of their probability.
 33. The method of claim 25wherein identifying the target cell is further based on a currenttraveling pattern of the user.
 34. The method of claim 25 furthercomprising transmitting the reminder for the task to the user via themobile communication device and to preventing a subsequent reminder forthe task unless at least one of a predetermined time thereafter hasexpired, and a distance between the user and the task cell has notreduced to zero, but has exceeded a threshold distance that is greaterthan the predetermined distance.
 35. The method of claim 24 wherein thetask is associated with a plurality of task locations located in one ormore task cells and determining the reminder position includes:identifying a target cell that is within a predetermined distance of acurrent position of the user; identifying one or more forward cells foreach of the one or more task cells, wherein for each task cell, the oneor more forward cells are in a trajectory leading from the target cellto the task cell; and identifying one or more backward cells for each ofthe one or more task cells, wherein for each task cell, the one or morebackward cells are in a trajectory from the target cell leading awayfrom the task cell.
 36. The method of claim 35 wherein determining thereminder position further includes: for a first task cell of the one ormore task cells one or more strong backward cells comprising backwardcells associated with the first task cell that are not identified asforward cells for other of the one or more task cells; calculating aforward probability of the user traveling from the target cell in atrajectory leading toward the first task cell by summing a number oftimes the user has transitioned from the target cell to any of the oneor more forward cells associated with the first task cell and dividingthe sum by a total number of transitions from the target cell;calculating a backward probability of the user traveling from the targetcell in a trajectory leading away from the first task cell by summing anumber of times the user has transitioned from the target cell to any ofthe one or more strong backward cells and dividing the sum by the totalnumber of transitions from the target cell; and designating the targetcell as a reminder position when the forward probability exceeds thebackward probability by the threshold value.
 37. The method of claim 35wherein determining the reminder position further includes: calculatinga forward probability of the user traveling from the target cell in atrajectory leading toward any task cell by summing a number of times theuser has transitioned from the target cell to any of the one or moreforward cells and dividing the sum by a total number of transitions fromthe target cell; calculating a backward probability of the usertraveling from the target cell in a trajectory leading away from anytask cell by summing a number of times the user has transitioned fromthe target cell to any of the one or more backward cells and dividingthe sum by the total number of transitions from the target cell; anddesignating the target cell as a reminder position when the forwardprobability exceeds the backward probability by the threshold value. 38.The method of claim 22 wherein the user specified task informationincludes a plurality of tasks and wherein the method further comprisesprioritizing the plurality of tasks based on at least one of taskimportance and completion time, and determining the reminder positionfor a task location associated with a task having a highest priority.39. The method of claim 38 wherein the method further includesdetermining a reminder position for respective task locations associatedwith each of the plurality of tasks in order of decreasing priority. 40.The method of claim 22 wherein the monitoring includes identifying thelocation of the mobile communication device at least one of at a fixedsampling interval and at a sampling interval proportional to at leastone of a velocity and an expected velocity of the mobile communicationdevice.
 41. A computer readable storage medium having stored programinstructions for providing a reminder of a task to be performed at atask location, the stored program instructions for performing a methodcomprising: monitoring a location of a user via a mobile communicationdevice associated with the user at predetermined time intervals fortracking historical travel information of the user; receiving userspecified task information that includes a task and a task location;storing the user's historical travel information and user specified taskinformation in a data store; determining a reminder position as aposition where an estimated probability of the user traveling from thereminder position at a particular time in a trajectory leading towardthe task location exceeds an estimated probability of the user travelingfrom the reminder position at that same time in a trajectory leadingaway from the task location by a threshold value; and generating areminder for the task when the reminder position is identified.
 42. Anapparatus for providing a reminder of a task to be performed at a tasklocation, the apparatus comprising: means for monitoring a location of auser via a mobile communication device associated with the user atpredetermined time intervals for tracking historical travel informationof the user; means for receiving user specified task information thatincludes a task and a task location; means for storing the user'shistorical travel information and user specified task information; andmeans for generating a reminder of the task when a reminder position isdetermined, wherein the reminder position is a position where anestimated probability of the user traveling from the reminder positionat a particular time in a trajectory leading toward the task locationexceeds an estimated probability of the user traveling from the reminderposition at that same time in a trajectory leading away from the tasklocation by a threshold value.